We propose a retrospective (historical) cohort study to determine the association of self-reported marijuana use with a variety of health outcomes, including respiratory disorders and injuries. The study cohort is composed of 79,200 members of the Kaiser Permanente Medical Care Program (KPMCP) who were age 15 to 49 years when they underwent multiphasic health checkups at two KPMCP facilities between 1979 and 1986, and completed questionnaires detailing their past and current use of tobacco products and of marijuana. We will ascertain mortality through 1992 using the California Automated Mortality Linkage System (CAMLIS). We will ascertain outpatient morbidity during a three-year period after the MHC by review of Kaiser Permanente medical records for doctor visits in 4,500 cohort members. We will perform analyses to determine the relationship of marijuana use to each of these outcomes. We will compare the relative risks associated with marijuana use across tobacco cigarette use strata (current, former, and nonsmoker), and stratify and adjust for other selected variables of interest, such as intensity and duration of marijuana and tobacco cigarette use, and use of alcohol. We will focus particularly on respiratory disorders and injuries for which there are data suggesting an association with marijuana use, but will systematically examine the relationship of marijuana to other categories of disease. The proposed study would be, to our knowledge, the first large-scale cohort study of the relationship of marijuana use to health outcomes, and should contribute greatly to our knowledge of the health effects of marijuana use. The study cohort has large numbers of marijuana users in all the strata of tobacco cigarette use, which will allow us to distinguish associations of marijuana use from those of tobacco cigarettes as well as to examine the association of the combined use of these substances to the outcome measures. The proposed study is particularly relevant since its results may impact on public health policy, because drug abuse is an extremely important public health problem and marijuana is by far the most commonly used illicit substance.